I've always had the attitude that if I saw a really good buck, I didn't want to worry about angling shot, neck shot or 90-degree cross-body--nor, to a reasonable degree, distance. So, I've tended to favor 30-caliber.
If I impose certain limitations, I'll happily use lesser cartridges. I've killed a lot of deer with a .243, but I was really picky about my shots, and I never shot at a running deer.
Today's bullets provide better material to work with, in the smaller diameters. In .22 stuff, there are now 70-grain (+/-) bullets that are dependable on deer. That said, however, I'd still limit myself against angling shots and longer distances.
Overall, though, a lot depends on circumstance. I've had deer lie down beneath my tree stand. I 99.99% could have collected supper with a .22Short. (Did you know that an old doe's skin will just twitch like crazy when you drop little pieces of bark on her? It took five minutes of doing just that before she finally went away to nap somewhere else.
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